Surface treatment method and apparatus thereof

ABSTRACT

Treatment baths for surface treatment of semiconductor wafers by dipping thereof into a treatment liquid are arranged in a treatment bath train. 
     One or more selected treatment baths among these treatment baths are constructed to have a plurality of unit treatment vessels. The treatment liquid in these treatment vessels is replaced successively one by one of the unit treatment vessels. The semiconductor wafers are dipped in the treatment liquid contained in that unit treatment vessel that is not being subjected at that moment to the replacement of the treatment liquid.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for treating surfacesof objects such as semiconductor wafers (hereinafter called "wafers" forsimplicity) and other small objects with chemical treatment liquid.

2. Description of the Prior Art

As well known in production processes of semiconductor devices, varioussurface treatments such as etching, removing of photoresist films, wafercleaning, etc, are repeated. An apparatus available for achieving aseries of such surface processings automatically is disclosed, forinstance, in Japanese Patent Laying Open Gazette No. 52-150974 (1977),wherein various treatment baths and a drier are arranged in a line and atransfer machine or conveying machine moving along the line is provided.Cassettes each holding a lot consisting of a plurality of wafers areheld by a handling mechanism of the transfer machine and dippedsuccessively in treatment liquids filled in the treatment baths. Suchtreatment sequence is carried out automatically in response to commandsignals supplied from a controller comprising a microcomputer andothers.

However, in the conventional treatment apparatus, the transport ofcassettes should be interrupted momentarily during replacement oraddition of the treatment liquids, which is required because of adeterioration of the treatment liquid due to the repeated dippings andthe lapse of time. For example, consider an apparatus, illustratedschematically in FIG. 1 as a conceptional overview thereof, in which aloader L, treatment baths P₁, W₁ . . . W₄, a drier D and an unloader ULare aligned along a transporting path of a transporting machine T sothat the treatments are carried out in the order of the alignment. Whenthe treatment liquid of the treatment bath P₂ is being replaced, thefollowing cassette to be dipped in the bath P₂ should be kept waiting inthe treatment bath W₁ positioned just before the bath P₂.

Therefore, the flow of the cassettes becomes intermittent, reducing theprocessing efficiency as a whole. Furthermore, during such replacementof the treatment liquid in one of the treatment baths, the deteriorationof treatment liquids continues to take place in all other baths,resulting in a significant problem of inhomogeneous surface treatmentsof wafers lot by lot. Further, the number of replacements of thetreatment liquids required for treatment of a certain number of lots isincreased due to the deterioration, resulting in a low economicalefficiency.

Especially, the integration density of integration circuits build up onsurfaces of semiconductor wafers has increased recently, therefore, aprovision of a dustfree atmosphere during formation of fine patterns anda uniform liquid quality control is important and is a big problem to besolved. To this end, liquids suffering rapid deterioration with time,for example, a cleaning liquid consisting of H₂ SO₄ and H₂ O₂, requiresfrequent replacement thereof and sometimes the replacement is necessaryfor every dipping of the wafers. Once the treatment liquid is drainedonce out of the bath, it takes a long time interval for cleaning of theinside of the bath, a supply of new liquid and the temperature increasethereof, while the bath cannot be used during such activity.

SUMMARY OF THE INVENTION

The present invention is directed to a surface treatment method of thebatch type for transporting an object to be treated along a treatmentsbath train including a predetermined number of treatment bath and fordipping said object in a treatment liquid supplied in said treatmentbaths in a predetermined order thereby to execute a surface treatment ofsaid object.

The surface treatment method according to the present inventioncomprises steps of: preparing a treatment bath train in which a desiredtreatment bath is constructed as a multi-vessel treatment bathcomprising a plurality of unit treatment vessel; and replacing thetreatment liquid in said multi-vessel treatment bath successively one byone in said unit treatment vessels and dipping said object in thetreatment liquid in the unit treatment vessel which is not beingsubjected to replacement of the treatment liquid at that moment.

Apparatus for performing the surface treatment method described above isalso provided in the present invention. As shown in the functional blockdiagram of FIG. 2, the apparatus comprises: a treatment bath train 11consisting of a predetermined number of treatment baths, in which atypical predetermined treatment bath is constructed as a multi-vesseltreatment bath 10 comprising a plurality of unit treatment vessels; asupplying and draining mechanism 12 for supplying and draining thetreatment liquid in each unit treatment vessel; a transporting means 13for transporting the object to be treated along said treatment bathtrain 11 and dipping the same in a predetermined order in the treatmentliquids in the said treatment baths; and a control means 14 for excutingthe transportation control of said transporting means 13 and thetreatment liquid control of said treatment bath train.

The control means comprises: first control means 15 for replacing thetreatment liquid in said multi-vessel treatment bath successively one byone in said unit treatment vessels through said supplying and drainingmechanism; and second control means 16 for generating command signalsfor dipping the object in the treatment liquid in the unit treatmentvessel not subjected at that moment to the replacement of the treatmentliquid thereof and for transmitting said command signals to saidtransporting means 13.

According to one aspect of the present invention, the surface treatmentmethod comprises the steps of: preparing a treatment bath traincomprising a multi-group of unit treatment vessel obtained by combiningtwo or more groups of unit treatment vessels; and replacing thetreatment liquid in said multi-group of unit treatment vesselssuccessively one by one of said groups of unit treatment vessel anddipping said object in the treatment liquid in the group of unittreatment vessel which is not subjected to the replacement of thetreatment liquid at that moment.

In an apparatus for practicing the preferred embodiment, the treatmentbath train comprises multi-group of unit treatment vessels constructedby combination of two or more groups of unit treatment vessel in which adesired plurality of unit treatment vessels are provided. A supplyingand draining mechanism supplies and drains the treatment liquid in eachunit treatment vessels of each group of unit treatment vessel. Alsoprovided is a control means for executing a control of a transportingmechanism which transports said object along said treatment bath trainand dips the same in a predetermined order in the treatment liquid inthe unit treatment vessels, and for executing a control of a treatmentliquid in said treatment bath train. The control means comprises firstcontrol means for replacing the treatment liquid in said group of unittreatment vessel successively one by one in said unit treatment vesselsthrough said supplying and draining mechanism, and second control meansfor generating command signals for dipping the object in the treatmentliquid in the unit treatment vessel belonging to the group of unittreatment vessels not being subjected at that moment to the replacementof the treatment liquid thereof and transmitting said command signal tosaid transporting means.

It should be noted that the term "replacement" or "replacing" of thetreatment liquid includes an addition or partial refilling thereof, inaddition to full replacement of the treatment liquid, while the term"multi-vessel" or "multi-group" mean any installment of two or morevessels or groups with any associated relation respectively, requiringnot necessarily a continuity in space, i.e., separated location of thecomponents being allowed.

Accordingly, an object of the present invention is to provide a surfacetreatment method and apparatus thereof for treating objects such assemiconductor wafers or other small objects with a treatment liquid, inwhich a delay in the processing of the objects, due to replacement anddraining of the treatment liquid, is not required and the surfacetreatment efficiency as a whole can be improved.

Another object of the present invention is to provide a surfacetreatment method and apparatus thereof, in which uniform surfacetreatment and high economical efficiency are obtained.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptional overview of a conventional surface treatmentapparatus,

FIG. 2 is a functional block diagram showing schematically theconstruction of an apparatus according to the present invention,

FIG. 3 is a conceptional overview of a surface treatment apparatusaccording to a first embodiment of the present invention,

FIG. 4 is a schematic diagram of a control system of a multi-vesseltreatment bath P₁ according to the first embodiment,

FIG. 5, FIG. 7A and FIG. 7B are flow charts of the operations of thefirst embodiment,

FIG. 6(a) and FIG. 6(b) are diagrams for explaining the symbols used inFIG. 5, FIG. 7A, FIG. 7B, FIG. 10, FIG. 11A and FIG. 11B,

FIG. 8 is a conceptional overview of a surface treatment apparatus usedin second embodiment,

FIG. 9 is a diagram showing a partial model of a multi-vessel treatmentbath P₁ in the second embodiment,

FIG. 10, FIG. 11A and FIG. 11B are flow charts showing the operations ofthe second embodiment,

FIG. 11 is a diagram showing a combination of FIG. 11A and FIG. 11B,

FIG. 12 is a timing chart for replacement of the treatment liquid,

FIG. 13 is a conceptional overview of a surface treatment apparatusaccording to third embodiment of the present invention, and

FIG. 14 is a conceptional overview of a surface treatment apparatus usedin a modified embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A. Construction of First Embodiment

FIG. 3 is a conceptional overview of a surface treatment apparatus forprocessing semiconductor wafers or substrates according to firstembodiment of the present invention, which executes the treatmentscorresponding to the aforementioned apparatus of FIG. 1. The apparatusof FIG. 3 is a multi-bath batch type surface treatment apparatus forknown RCA cleanings, which is described, for example, at page 63 andlater in the "Review of Overall Technologies for Automation Systems ofModern Semiconductor Plants", issued by Science Forum Co., Ltd. 25thJuly 1984. The conventional apparatus of FIG. 1 is used similarly forthe RCA cleanings and the following treatments are achieved in thetreatment bath train.

    ______________________________________                                        Treatment bath P.sub.1                                                                      Cleaning by ammonia and hydrogen                                              peroxide solution                                               Treatment bath P.sub.2                                                                      Cleaning by diluted fluoric acid                                Treatment bath P.sub.3                                                                      Cleaning by hydrochloric acid and                                             hydrogen peroxide solution,                                     Treatment baths W.sub.1 ˜W.sub.4                                                      Rinsing by pure water                                           ______________________________________                                    

On the other hand, in an embodiment of the present invention in FIG. 3,the treatment baths P_(I), P_(II) and P_(III) corresponding to thetreatment baths P₁, P₂, P₃ of FIG. 1 are formed as multi-vesseltreatment baths comprising respective pairs of the unit treatmentvessels (P_(1A),P_(1B)), (P_(2A),P_(2B)) and (P_(3A),P_(3B)) for storingthe same treatment liquid respectively. Therefore, the followingtreatments are carried out in each unit vessel.

    ______________________________________                                        Unit treatment vessels P.sub.1A, P.sub.1B                                       Cleaning by ammonia and hydrogen                                              peroxide solution                                                           Unit treatment vessels P.sub.2A, P.sub.2B                                       Cleaning by diluted fluoric acid                                            Unit treatment vessles P.sub.3A, P.sub.3B                                       Cleaning by hydrogen peroxide solution                                      ______________________________________                                    

In the multi-vessel treatment bath P_(I), the treatment liquids in theunit treatment vessels P_(1A) and P_(1B) are replaced alternately. Ifthe unit treatment vessel P_(1A) is found in waiting status due to thereplacement of the treatment liquid, the cassette holding a lot ofsemiconductor wafers as the object to be treated is dipped in thetreatment liquid stored in another unit vessel P_(1B), which is notbeing subjected at that time to replacement of the treatment liquidtherein. The same selection rule of the unit vessel for dipping isapplied similarly to the other multi-vessel treatment bath P_(II),P_(III).

Moreover, there is no need of replacement for the treatment liquid forthe treatment baths W₁ ˜W₄, which are rinsing baths with continuousoverflow of pure water. Therefore, these baths are not constructed asmulti-vessel treatment baths, but as single treatment baths, similar tothe apparatus shown in FIG. 1. The loader L, the drier D, the unloaderUL and the transporting machine T are also located in the bath trainsimilarly to that of the apparatus of FIG. 1.

FIG. 4 is a schematic diagram of the control system for the multi-vesseltreatment bath P_(I) of FIG. 3. As explained above, the bath P_(I)consists of two unit vessels P_(1A), P_(1B). A mixing tank M₁ for mixingchemicals to prepare the treatment liquids is positioned on these unitvessels. The treatment liquid prepared therein is supplied into the unitvessels P_(1A), P_(1B) respectively through solenoid valves 1a, 1b aspart of the liquid supplying and draining mechanism thereof. The usedtreatment liquid is drained through solenoid valves 2a, 2b provided atthe bottom of the unit vessles P_(1A), P_(1B).

All these solenoid valves 1a, 1b, 2a, 2b are connected to and controlledby a control circuit 3 consisting of microcomputers, sequencers andothers, which comprises CPU 3a and a memory 3b. The control circuit 3 isconnected in turn to the transporting machine T, the loader L, the othertreatment baths W₁ . . . , the drier D and the unloader UL, in additionto an input/output device 4 such as a keyboard and a CRT. Particularlyfor the multi-vessel treatment baths P_(II), P_(III) among respectivetreatment bath W₁ . . . , the control circuit 3 is connected to thesolenoid valves for supplying and draining the treatment liquid in eachunit treatment vessel, similarly to the treatment bath P_(I). Throughthese connections, the control circuit 3 carries out the control oftransportation and replacement of treatment liquids, which will bedescribed later. Of course, metering of liquid components and control ofthe liquid temperature are also carried out, though the mechanismthereof is not shown in FIG. 4.

B. Procedures for Replacement of Treatment Liquid in the FirstEmbodiment

The replacement procedures in the first embodiment will now bedescribed, separately for procedures before dipping of first lot(initial stage) and for subsequent procedures (normal stage). Theprocedures belong to a control routine through the control circuit 3 ofFIG. 4.

B-1 Procedures for Replacement of Treatment Liquid at the Initial Stage

The following description is made with reference to FIG. 5 showing aflow chart for replacing of treatment liquid at the initial stage. Inthe following description, the term "forward vessel" means a unit vesselpositioned at the side of the loader L (i.e. a forward side) and theterm "backward vessel" means a unit vessel positioned at the side of theunloader UL (i.e. a backward side). The liquid storage states in eachunit treatment vessel in the main steps of the control sequence areshown schematically in FIG. 5 and other flow charts. The meanings of thesymbols used for representing the storage states are shown in FIG. 6(a),i.e., the arrow marks from the upper side indicate supply of thetreatment liquid, while the arrow marks to the lower side indicatedrainage thereof. Moreover, hatching in the unit vessel representsstorage of the treatment liquid. The following description will be givenfor only one multi-vessel treatment bath, but is applicable similarlyfor the other multi-vessel treatment baths belonging to the bath train.

At first, in the step S1 of FIG. 5, it is judged whether the treatmentliquid is stored or not in the forward vessel, and if stored, thetreatment liquid is drained in the step S2. Then, the storage of thetreatment liquid is judged for the backward vessel and the treatmentliquid if stored is similarly drained (step S3, S4). Therefore, both theforward and backward vessels are vacant at the moment when the step S4is over. The judgement for storage of treatment liquid in the abovesteps may be achieved with reference to flags being set up in registers(not shown) or other elements within the control circuit 3 forindication of the storage state of the treatment liquid in each unitvessel.

Then, the treatment liquid is supplied to the forward vessel in thefollowing step 5 while the temperature control is also carried out. Theavailability of this forward vessel is registered through a setting of aflag and it is declared that the forward vessel is found in the use.Namely, the control is so designed that the dipping of the cassette isalways started from the forward vessel at the initial stage. In step S6,a cassette acceptable signal indicating a acceptable condition of thecassette is transmitted to the control unit (not shown) of thetransporting machine T to terminate the routine at the initial stage.

B-2 Procedures for Replacement of Treatment Liquid in the Normal Stage

The replacing procedures of treatment liquid in the normal stage (FIG.7A and FIG. 7B) will now be described. These control procedures takeplace in parallel with the transporting and dipping procedures of thecassettes, which will be described later. At first, in the step S11 ofFIG. 7A, it is estimated and judged whether when the next lot is dippedin the treatment liquid in a unit vessel currently found in the use,expected number of treatments corresponding to the total namber of lots(more precisely, the total number of wafers) dipped in the treatmentliquid in the unit vessel will remain below the maximum value allowedfor the treatment liquid. The maximum value is stored previously in thememory 3b of the control circuit 3 or others.

If the expected number of treatments will exceed the maximum value, theroutine proceeds to step S14. On the other hand, if the expected numberwill remain below the maximum value, there is no need of the replacementfor treatment liquid and it is estimated in the next step S12 whetherthe treatment of the next lot in the unit vessel can be completed or notwithin the remaining life time of the treatment liquid currently used.Of course, it is necessary to store in memory 3b previously a life timevalue of the treatment liquid and an estimate of the time period (i.e.,standard time) required for the dipping. It is also necessary to countby a timer the time lapse from the previous replacement of the treatmentliquid.

If it is judged that the treatment in the unit vessel can be completedwithin the remaining life time, the remaining life time is compared inthe next step S13 with the expected time required for replacing thetreatment liquid. If the remaining life time is equal to or longer thanthe time required for replacing the treatment liquid, there is no needof the replacement at the current stage and thus the routine iscompleted without the replacement. On the other hand, if the remaininglife time is shorter than the time required for replacing the treatmentliquid, the step is forwarded to the step S14, where it is judgedwhether an instruction signal for replacing the treatment liquid isgiven or not. The aforementioned instruction signal for replacing thetreatment liquid is generated in the control circuit 3 to indicatewhether the routine following the step S15 for replacing the treatmentliquid should be actually started or not, taking the running conditionof the overall system into consideration. The control may be arranged insuch a manner that the routine of FIG. 7A is not started if there are noinstructions for replacing the treatment liquid, in place of the aboveindicated procedure.

If there are no instructions for starting the routine of replacing thetreatment liquid, the replacement does not take place, while if theinstruction is found, it is judged in the next step S15 whether theforward vessel is in or after the use. If the forward vessel is found inor after the use, the treatment liquid is supplied in the next step S16to the backward vessel being kept at waiting and the availability of thebackward vessel is registered.

If the forward vessel is found not in or after the use, the forwardvessel is retained in the waiting condition and reversely the backwardvessel is in or after the use. Therefore, the treatment liquid issupplied to the forward vessel in the step S17 and the availability ofthe forward vessel is registered. When either the step S16 or the stepS17 is over, it is normally found that the treatment liquid is stored inboth of the forward and backward vessels.

In the next step S18 of FIG. 7B, it is judged whether there is a lotbeing dipped at that moment in the corresponding treatment bath. Thisjudgment may be achieved, for example, by referring detection signalsindicating the presence or the absence of the cassette supplied from aphotoelectric sensor (not shown) located near an upper part of thetreatment bath or signals from the routine to control the transportingmachine T. If there is any lot under treatment, the waiting condition isset. On the other hand, if there are no lots or the lot disappears, itis judged in the next step S19 whether the forward vessel is availableor not, in other words, a new supply of the treatment liquid has beensupplied to the forward vessel or not. This is identical with thejudgement whether the step S17 is executed or not. If the forward vesselis available, it is declared in the step S20 that the forward vessel isnow in use and then it is judged in the step S21 whether the treatmentliquid is stored or not in the backward vessel. If stored, the treatmentliquid is drained in the step S22.

On the other hand, if it is judged in the step S19 that the forwardvessel is not available, it is judged in the step S23 whether thebackward vessel is now available or not. If either the forward or thebackward vessel is not available, the routine is returned to the stepS15 of FIG. 7A to supply the treatment liquid to one of the two vessels.On the other hand, if the step S16 has been executed and the backwardvessel is available, the steps S24-S26 obtained by interchanging the"forward vessel" and the "backward vessel" in the steps S20-S22 areexecuted and the treatment liquid in the forward vessel is drained.

When the treatment liquid is supplied to any one unit vessel and it isdeclared that the unit vessel is in the use while the other unit vesselin use up to that time moment is perfectly drained, the sequence isadvanced to step S27. In the step S27, the control conditions of thetreatment liquid is reset and at the same time the stop or theinterruption of the other processing is released. Thereafter, in thestep S28, a signal indicating the acceptability of the cassette isgenerated and transmitted to the transporting machine T and the routineis completed. These routines may be repeated appropriately.

C. Dipping Procedures in the First Embodiment

In parallel to such replacing procedures of the treatment liquid, thetransporting and dipping procedures of the lot consisting of, forexample, twenty-five semiconductor wafers, are executed. Theconstruction used for conventional apparatus may be applied directly forthe transporting machine T and individual dipping sequences. Aprocessing characteristic in this embodiment is a selection procedure ofthe unit vessel to be used for the dipping. The selection procedure maybe executed by detecting the unit vessel for which a declaration of useis found under the condition that the cassette acceptable signal isoutputted, and then generating and outputting a command signalindicating the declared vessel to the transporting mechanism T. Onreceiving the command signal, the transporting mechanism T transportsthe cassette to the indicated unit vessel and dips the same in thetreatment liquid in the unit vessel.

As described above, in this embodiment, the treatment liquid is replacedin the forward and backward vessels alternatively and the lot is dippedalternatively in the treatment liquid in the unit vessel in which newtreatment liquid has been supplied. The dipping time period of the lotin the treatment liquid in each unit vessel depends upon the chemicalquality of the treatment liquid.

Second Embodiment

D. Construction of the Second Embodiment

The second embodiment of the present invention will be described.Corresponding to the treatment baths P_(I), P₂ and P₃ of FIG. 1, thesecond embodiment of FIG. 8 is provided with the multi-vessel treatmentbaths Q_(I) ˜Q_(III), which consist of respective three unit vessels(P_(1A), P_(1B), P_(1C)), (P_(2A), P_(2B), P_(2C)) and (P_(3A), P_(3B),P_(3C)). The solenoid valves 1a-ic, 2a-2c are also attached to eachtreatment bath, as shown in FIG. 9. The difference between the first andsecond embodiments is found in the fact that not only the number of theunit vessels is increased, but one among two unit vessels (e.g., P_(1A)and P_(1B) in FIG. 9) is filled with a treatment liquid with relativelyshort time lapse from the supply thereof ("new liquid"), while the othervessel is filled with treatment liquid with relatively long time lapsefrom the supply thereof ("old liquid"). When a new treatment liquid issupplied to the unit vessel (e.g., P_(1C) in FIG. 9) found at thewaiting condition, the old liquid is drained while the treatment liquidconsidered as the new one up to that moment is, in turn, considered asan old liquid.

Thus, a new liquid vessel, an old liquid vessel and a waiting vessel areprepared cyclically and the lot is dipped in the old liquid at that timemoment and then redipped in the new liquid, assuring nearly the samequality surface treatment to any lot, regardless of the timing when thelot is transported in the corresponding treatment bath. Therefore, it ispossible to avoid fluctuation of treatment quality in accordance withthe deterioration stage of the treatment liquid at the time moment ofthe lot dipping.

E. Procedures for Replacement of Treatment Liquid in the SecondEmbodiment

E-1. Procedures for Replacement of Treatment Liquid at Initial Stage

As with the first embodiment, the procedures for replacement of thetreatment liquid at the initial stage will be described first. Forbetter understanding of the second embodiment, symbols shown in FIG.6(b) are used in the operation flows thereof (FIG. 10, FIG. 11A and FIG.11B). Namely, the three unit vessel are referred as "A vessel", "Bvessels" and "C vessel" successively from the side of the loader L andthe new liquid is indicated by full hatching in the symbols, while theold liquid is indicated by partial hatching.

In FIG. 10, showing the replacing procedures at the initial stage, it isjudged at first in the step S31 whether the treatment liquid is storedor not in the A and/or B vessel. If stored, the treatment liquid isdrained in the next step S32 from the unit vessel storing the treatmentliquid. If the treatment liquid is stored in both the A and B vessels,the treatment liquid in both vessels are drained. It is supposed in FIG.10 that the treatment liquid is stored in the B and C vassels.Therefore, in this example, the treatment liquid is drained from the Btank. In the step S33, the treatment liquid is supplied to the A and Bvessels and then, it is judged in the step S34 whether the temperatureadjustment is completed and the dipping preparation for receiving a lotis over or not.

When the dipping preparation is completed, it is registered in the stepS35 that the both A and B vessels are available and the signalsindicating a cassette acceptable signal are output in the step S36.Furthermore, the liquid in the C vessels is drained in the step S37 andthe control condition of the treatment liquid is reset for the C vesselin the step S38. The C vessel is returned to the waiting state in thestep S39 to complete the initial routine. Therefore, when the initialroutine is completed, both of the A and B vessels are ready for dippingany lot.

E-2 Procedures for Replacement of Treatment Liquid at the Normal Stage

FIG. 11A and FIG. 11B are partial flow charts showing the replacingprocedures at the normal stage, and they are combined as shown FIG. 11to form a signal flow chart. It is judged in the step S41 of FIG. 11Awhether A and B vessels are those found presently in use or not. If yes,the routine is forwarded to the step S42. As clearly understood from theroutine described later, the treatment liquid is cyclically replaced inthe order of the A, B and C vessels. Therefore, when the A and B vesselsare in use, it is understood that a new liquid or liquid considered asnew is stored in the B vessel.

In the next step S42, it is judged whether the status values indicatingdip processing progress, such as the finish time of the treatment andthe total number of the dips reach the conditions reserved for startingthe replacing of the treatment liquid of the A vessel, such as theremaining life time and the allowable maximum number of treatments whenthe next lot is dipped without a replacement of the liquid. Thisjudgment corresponds to the steps S11-S13 of FIG. 7A.

If it is found that these conditions are satisfied, the treatment liquidis supplied to the C vessel at the waiting condition for preparing thedipping. When the preparation is over, the availability of the B and Cvessel is registered (the step S43-S45). Then, the lot acceptable signalis output and the liquid in the A vessel is drained (the step S46, S47).Therefore, from that moment, the treatment liquid in the B vessel isconsidered as old while the treatment liquid in the C vessel isconsidered as new.

After resetting the control condition of the treatment liquid in the Avessel, the emptied A vessel is set at the waiting condition (the stepS48, S49), completing the routine for the first cycle.

When the routine is repeated again from the threshold thereof, the oldand new liquids are found in the B and C vessels respectively.Therefore, the steps S52-S59 of FIG. 11B are executed through the stepsS41 and S51. These steps S52-S59 correspond to the aforementioned stepsS42-S49, in which the A, B and C vessels are cyclically shifted by onevessel. Thus, if the step S59 is over, the old and new liquids are foundin the C and A vessels respectively at this time.

At the third cycle, the routine reachs to the step S61 of FIG. 11Bthrough the steps S41 and S51, and the steps S62-S69 with similar cyclicpermutation are further executed and then the A vessel is filled withold liquid while the B vessel is filled with new liquid.

In summary, the following three conditions are repeated cyclically.

    ______________________________________                                        A (old liquid),                                                                            B (new liquid),                                                                             C (waiting)                                        A (waiting), B (old liquid),                                                                             C (new liquid)                                     A (new liquid),                                                                            B (waiting),  C (old liquid)                                     ______________________________________                                    

FIG. 12 is a time chart showing the above repetition, wherein the newand old liquid are indicated by a white band and a hatchied bandrespectively. Furethermore, the symbols "S", "D" and "W" indicate"supply", "drain" and "waiting", respectively. As clearly understoodfrom FIG. 12, unit vessels containing the new and old liquid are alwaysfound, while the remaining vessel is kept at the waiting condition.Moreover, there is a slight difference between the supply starting timet₁ of the treatment liquid of one vessel and the drain starting time t₂of the another vessel, because the processing of FIG. 11A and FIG. 11Bdefines the sequence, in which the drain is started after the supply isover. The time duration of each condition in the time chart depends uponthe incoming frequency of lots.

F. Dipping Procedures of the Second Embodiment

In this embodiment, the treatment liquid is replaced cyclically so thatthe lot is dipped in the old and new liquid, the dipping time thereofbeing determined by the character or the condition of the treatmentliquid. For example, if the dipping time period in the old and newliquid is t_(a) and t_(b) respectively, the condition t_(a) >t_(b) ort_(a) =t_(b) may be allowed according to the quality or the character ofthe treatment liquid and other. Namely, it is possible to preset t_(a)and t_(b) appropriately by taking the character of the liquid intoconsideration. Thus, any lot can be treated with the treatment liquidhaving a nearly constant chemical effectivity, assuring the uniformityof treatment of the objects. As with the first embodiment, the presenceor the absence of the registration of use is referred to in order tojudge what unit vessel should be used for dipping. It is easy to checkwhich treatment liquid is old, if the aforementioned cycling order isestablished previously.

Moreover, while one lot is dipped in the new liquid, the next lot may bedipped in the old liquid. In this case, it is unnecessary to keep thelot in the waiting condition thereof and overall flow of the lotsbecomes smooth.

Third Embodiment

G. Construction of the Third Embodiment

FIG. 13 is a schematic overview of the third embodiment of the presentinvention. In this apparatus, among the treatment baths of aconventional apparatus shown in FIG. 1, a plurality of the treatmentbaths (unit treatment vessels) corresponding to, for example, thetreatment baths P₁, W₁, P₂, W₂, P₃ and W₃, are arranged one by one toprovide three unit groups of unit treatment vessels; P_(A), P_(B) andP_(C), which are composed as follows;

    ______________________________________                                        P.sub.A = (P.sub.1A, W.sub.1A, P.sub.2A, W.sub.2A, P.sub.3A, W.sub.3A)        P.sub.B = (P.sub.1B, W.sub.1B, P.sub.2B, W.sub.2B, P.sub.3B, W.sub.3B)        P.sub.C = (P.sub.1C, W.sub.1C, P.sub.2C, W.sub.2C, P.sub.3C,                  ______________________________________                                        W.sub.3C)                                                                 

These three unit groups of unit treatment vessels, P_(A), P_(B) andP_(C) are successively associated to provide the multi-group oftreatment vessels (P_(A) +P_(B) +P_(C)).

In other words, the multi-vessel treatment bath is composed by aplurality of unit treatment vessels in the first and second embodiment,while the multi-group of treatment vessel is composed by a plurality ofthe unit groups of treatment vessels or unit groups of treatment bath.

The loader L, the treatment bath W₄ and the drier D are used commonlyfor every baths belonging to a treatment bath train. Each unit treatmentbath in each unit group of treatment baths P_(A), P_(B), P_(C) isprovided with solenoid valves and the related piping for supplying anddraining the treatment liquid as described in the earlier discussions ofthe first and second embodiments.

One among the three unit groups of treatment vessels P_(A), P_(B), P_(C)is used for waiting for the replacement of the treatment liquid and thelot is dipped successively in the remaining two unit groups of treatmentvessels. The former one unit group of treatment vessels for the waitingis selected cyclically among the three unit groups of treatment vesselsP_(A), P_(B), P_(C), as was the selection of one among three unittreatment vessels in the second embodiment.

The unit groups of treatment vessels P_(A), P_(B), P_(C) may constructedby a required plurality of the treatment vessels, not limited to theaforementioned construction.

H. Replacing Procedures of Treatment Liquid

The fundamental operating procedures of this third embodiment areobtained by reading each unit treatment vessels A, B and C in FIG. 10,FIG. 11A and FIG. 11B as the unit groups of treatment vessel P_(A),P_(B) and P_(C) respectively.

However, the status judgment of the treatment liquid in each unit groupof treatment vessels is executed by overall judgment of the respectivestatus of the treatment liquid in each unit treatment vessel (other thanwater rinsing baths) belonging to the corresponding unit group oftreatment vessels. For instance, when the status values such as the lifetime and the dipping number of the treatment liquid in at least one (forexample, P_(1A)) among unit treatment vessels belonging to one unitgroup of treatment vessels (for example, P_(A)) reach the valuespredetermined for the replacing, the unit group of treatment vessels(P_(A)), as a whole, is switched over to the waiting status. In thiswaiting status, all liquid in respective unit treatment vesselsbelonging to the unit group of treatment vessels (P_(A)) is drained andreplaced with new liquid. As described with respect to the secondembodiment, it is not necessarily required that old and new liquid areprepared and the lot is dipped at first in the unit group of treatmentvessels containing the old liquid. Other modifications described for thefirst and second embodiment are also applicable in connection with thisembodiment.

The dipping procedures for this embodiment will be clearly understoodfrom the aforementioned description, therefore, further explanation isomitted.

Modifed Embodiments

The present invention is not limited to the aforementioned embodiments,and the following modifications may be applied to the present invention.

(1) The number of the unit treatment vessels composing the multi-vesseltreatment bath may be more than four. If the dipping times in themulti-vessel treatment baths are different from each other, each of themulti-vessel treatment baths can comprise a different number of the unittreatment vessels. For instance, suppose that the dipping continues fort, 2t and 3t minutes in the multi-vessel treatment baths R_(I), R_(II)and R_(III) of FIG. 14, respectively. In this case, as shown in FIG. 14,the multi-vessel treatment baths R_(I), R_(II) and R_(III) areconstructed of two (P_(1A), P_(1B)), three (P_(2A), P_(2B), P_(2C)) andfour (P_(3A), P_(3B), P_(3C), P_(3D)) unit treatment vessels,respectively. In this situation, one of the unit vessels belonging toeach multi-vessel treatment bath is cycliclly selected to be used as awaiting bath while the dipping time in the other unit treatment vesselsis set to t min each, thereby to obtain the desired total dipping time.An effect similar to that of the aforementioned second embodiment willbe realized by constructing the multi-vessel treatment bath with thenumber of the unit treatment vessels corresponding to the time requiredfor the dipping and by setting the dipping time to each unit treatmentvessel to be identical each other.

(2) In the above embodiment, the time moment for replacing isdetermined, taking the life time of the treatment liquid and the dippingnumber of the lot into consideration. If it is known, however, that thelots are taken in at nearly the same time interval, the time moment canbe determined by only one aforementioned factor taking place earlier.

(3) In the above embodiment, the waiting vessel is kept empty up to thetime moment just before the start of draining the other unit treatmentvessel, in order to avoid deterioration of the treatment liquid duringthe waiting. However, it is also possible to set the unit vessel inwaiting after the supply of the treatment liquid. Namely, when thetreatment liquid requires a relatively long time for the temperaturecontrol and other factors, the treatment liquid may be supplied withouta long delay after the drain and the unit treatment vessel may be keptin waiting with the progress of such operations. Moreover, the supplyingand draining of the treatment liquid can be carried out manually orsemi-automatically.

(4) In the aforementioned first and second embodiments, three processingtanks P_(I) ˜P_(III) are constructed as the multi-vessel treatment bath,however, it is not inhibited to construct a part thereof as themulti-vessel treatment bath.

Particularly in a cleaning treatment bath, which decomposes organicsubstances adhered on the surface of a seniconductor wafers with a mixedliquid of H₂ SO₄ and H₂ O₂ at temperature higher than 100° C., theliquid quality is deterioratied quickly by the time lapse only.Therefore, the treatment liquid should be fully replaced every one ortwo dippings of the wafers. In such a case, only the treatment bath forsuch treatment liquid can be constructed by two or more unit treatmentvessels. Furthermore, this invention can be applied to any treatmentbath train consisting of one type of treatment bath only.

(5) Any combination of the aforementioned drying and other processingswith chemical treatment in the treatment bath is allowed. This inventionis applicable to full replacing of the treatment liquid and to partialreplacement such as addition of some amount thereof. Types of objects tobe treated and objects of the surface treatments impose no limitation tothis invention, which is also applicable to general platings in additionto surface treatment of glass substrates for photoetchings.

(6) FIG. 4 and FIG. 6 show the multi-vessel treatment bath integrallyassociated in spaced relation, however, the baths may be installedseparately.

According to this invention as described above, a required treatmentbath or a plurality of required treatment baths are constructed as amulti-vessel treatment bath or a multi-group of unit treatment vesselswhile the replacing of the treatment liquid is executed successively byunit treatment vessels or a unit group of unit treatment vessel.Therefore, the unit treatment vessel or the group thereof for which thereplacing operation is not currently executed can be found at all times,making unnecessary the waiting operation of the objects to be treatedand improving overall efficiency of the surface treatments. There aresubstantially no deteriorations of the treatment liquid in the treatmentbaths due to the waiting of the objects, thus enabling realization of aneconomical surface treatment method and apparatus. The surface treatmentof the objects may be executed more uniformly, as compared withconventional methods.

Particularly for objects in current demand such as semiconductor waferswith high integration density, it is sometimes required that thetreatment liquid shoud be replaced with new liquid for each dippingoperation. Further, in case treatment liquids with quick deteriorationcharacter should be used, the liquids sometimes must be replaced withoutany dipping due to the deterioration caused only by the time lapse. Ifthis invention is applied in such cases, a continuous surface treatmentis assured by constructing the required treatment baths as multi-vesseltreatment baths comprising a plurality of unit treatment vessels. Thereis then no need for keeping the objects to be treated in waiting duringthe time span required for draining the treatment liquid and cleaningthe bath to improve the productivity. If there are two or more treatmentbaths with high replacement frequency, the treatment efficiency can beimproved further by constructing these baths as multi-vessel treatmentbaths. The surface treatments under the same condition can thus assureuniform quality of the treated objects.

When predetermined numbers of the treatment baths or predeterminedgroups thereof are constructed as the multi-vessel treatment bath or agroup thereof, the space required for clean rooms and others is reducedwith higher productivity and better quality of the treatment.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A surface treatment method of batch type fortransporting an object to be treated along a treatment bath trainincluding a predetermined number of treatment baths and for dipping saidobject in a treatment liquid supplied in said treatment baths in apredetermined order, thereby to execute a surface treatment of saidobject, said surface treatment method comprising the steps of:preparinga treatment bath train comprising a plurality of treatment baths, inwhich a desired treatment bath is constructed as a multi-vesseltreatment bath comprising a pair of unit treatment vessels each of whichcontains the same treatment liquid; replacing the treatment liquid inone of said unit treatment vessels every time that predeterminedconditions are satisfied in such a manner that at least one of said pairof unit treatment vessels at all times contains said treatment liquidfor allowing said surface treatment of said object therein; andtransporting said object along said treatment bath train to dip saidobject in the treatment liquid in only one of the pair of unit treatmentvessel which is not being subjected to the replacement of treatmentliquid, a dipping time period in each unit treatment vessel of saidmulti-vessel treatment bath being determined according to acharacteristic of the treatment liquid therein.
 2. A surface treatmentmethod of batch type for transporting an object to be treated along atreatment bath train including a predetermined number of treatment bathsand for dipping said object in a treatment liquid supplied in saidtreatment baths in a predetermined order, thereby to execute a surfacetreatment of said object, said surface treatment method comprising thesteps of:preparing a treatment bath train comprising a plurality oftreatment baths in which a selected treatment bath is constructed ofthree or more unit treatment vessels each of which contains the sametreatment liquid, and one among said unit treatment vessels iscyclically selected for replacing the treatment liquid thereof everytime when predetermined conditions are satisfied; dipping said objectsuccessively in the treatment liquid in a unit treatment vessel of saidselected treatment bath in which the treatment liquid has been replacedearliest among all other unit treatment vessels of said selectedtreatment bath not being subjected at that moment to the replacement ofthe treatment liquid, a dipping time period in each unit treatmentvessel of said selected treatment bath being determined according to acharacteristic of the treatment liquid therein; and replacing thetreatment liquid in said selected treatment bath successively one by oneof said unit treatment vessels.
 3. A surface treatment method inaccordance with claim 1, whereinsaid object is dipped successively fromthe treatment liquid in the unit treatment vessel in which the treatmentliquid has been replaced earliest among all unit treatment vessels notsubjected at that moment to the replacement of the treatment liquid. 4.A surface treatment method of batch type for transporting an object tobe treated along a treatment bath train including a predetermined numberof multi-vessel treatment baths and for dipping said object in atreatment liquid supplied in said multi-vessel treatment baths in apredetermined order, thereby to execute a surface treatment of saidobject, said surface treatment method comprising the steps of:preparinga treatment bath train comprising a plurality of multi-vessel treatmentbaths in which each of said multi-vessel treatment baths is constructedto have a number of unit treatment vessels corresponding to the timerequired for the dip of said object therein, a dipping time in each unittreatment vessel being identical for each of said multi-vessel treatmentbaths; replacing the treatment liquid in each of said multi-vesseltreatment baths successively one by one of said unit treatment vesselsthereof; and transporting said object along said multi-vessel treatmentbaths to dip said object in the treatment liquid in a unit treatmentvessel thereof which is not being subjected to the replacement of thetreatment liquid at that moment while one of said unit treatment vesselsis being subject to replacement.
 5. A surface treatment method of batchtype for transporting an object to be treated along a treatment bathtrain including a predetermined number of treatment baths and fordipping said object in a treatment liquid supplied in said treatmentbaths in a predetermined order, thereby to execute a surface treatmentof said object, said surface treatment method comprising the stepsof:preparing a treatment bath train comprising a multi-group of unittreatment vessels formed of combining two or more groups of unittreatment vessels, said multi-group of unit treatment vessels beingconstructed as a pair of groups of unit treatment vessels and thetreatment liquid being replaced alternatively for said pair of groups ofunit treatment vessels every time when predetermined conditions aresatisfied while said object is dipped in the treatment liquid in thegroup of unit treatment vessels not being subjected at that moment tothe replacement of the treatment liquid therein; replacing the treatmentliquid in said multi-group of unit treatment vessels successively one byone of said groups of unit treatment vessels; and transporting saidobject along said treatment bath train to dip said object in thetreatment liquid in the group of unit treatment vessels which is notbeing subjected to replacement of the treatment liquid contained thereinwhile one of said groups of unit vessel treatment vessels is beingsubject to replacement at that moment.
 6. A surface treatment method ofbatch type for transporting an object to be treated along a treatmentbath train including a predetermined number of treatment baths and fordipping said object in a treatment liquid supplied in said treatmentbaths in a predetermined order, thereby to execute a surface treatmentof said object, said surface treatment method comprising the stepsof:preparing a treatment bath train comprising a multi-group of unittreatment vessels obtained by combining two or more groups of unittreatment vessels, said multi-group of unit treatment vessels beingconstructed to have three or more groups of unit treatment vessels andone group thereof being cyclically selected for replacing the treatmentliquid every time when predetermined conditions are satisfied while theremaining groups of unit treatment vessels are used for dipping theobject; replacing the treatment liquid in said multi-group of unittreatment vessels successively one by one of said groups of unittreatment vessels; and transporting said object along said treatmentbath to dip said object successively into the treatment liquid in eachunit treatment vessel belonging to the group of unit treatment vesselsin which the treatment liquid has been replaced earliest among all ofsaid groups of unit treatment vessels not being subjected at that momentto the replacement of the treatment liquid.
 7. A surface treatmentmethod of batch type for transporting an object to be treated along atreatment bath train including a predetermined number of treatment bathsand for dipping said object in a treatment liquid supplied in saidtreatment baths in a predetermined order, thereby to execute a surfacetreatment of said object, said surface treatment method comprising thesteps of:preparing a treatment bath train comprising a multi-group ofunit treatment vessels obtained by combining two or more groups of unittreatment vessels, said multi-group of unit treatment vessels beingconstructed to have three or more groups of unit treatment vessels andone group thereof being cyclically selected for replacing of thetreatment liquid contained therein every time that predeterminedconditions are satisfied while the remaining groups of unit treatmentvessels are used for dipping the object; replacing the treatment liquidin said groups of unit treatment vessels successively one by one of saidgroups of unit treatment vessels; and transporting said object alongsaid treatment bath to dip said object successively into the treatmentliquid in each unit treatment vessel belonging to the group of unittreatment vessels in which the treatment liquid has been replacedearliest among all of said groups of unit treatment vessels not beingsubjected at that moment to the replacement of the treatment liquidwhile one of said groups of unit treatment vessels is being subject toreplacement.
 8. A surface treatment method in accordance with claim 2,wherein:the number of said unit treatment vessels in said desiredtreatment bath is determined in correspondence to the time required fordipping of the object therein, a dipping time in each unit treatmentvessel being identical for each multi-vessel treatment bath.